1. Field of the Invention
The invention relates to semiconductor technology and more particularly to devices capable of damage detection.
2. Description of the Related Art
FIG. 1 is a local top view of a semiconductor wafer comprising dice 10 separated by scribe lines 20 and 30. Each die 10 comprises a seal ring 11 around the outer periphery thereof to protect against moisture, mechanical damage, electrostatic damage, and other dangers. Floating metal blocks 21 and 31 are formed in the dielectric based scribe lines 20 and 30 for specific tasks, such as serving as an alignment mark.
In a die separation step, also known as die singulation, a diamond-blade dicing saw cuts the wafer along the scribe lines 20 and 30 and separates the wafer into individual dice 10. When the diamond blade contacts the harder and tougher metal blocks 21 and 31 during die separation, the diamond blade may vibrate and deviate, applying stress to the neighboring dice 10. Of course, the seal rings 11 are designed to protect the dice 10 from the stress. In semiconductor technology materials with a low dielectric constant (lower than 3), also known as low-k dielectrics, are introduced in wafer fabrication and utilized as inter-layer dielectrics. The mechanical strength of the low-k dielectrics is much lower than the conventional dielectric, silicon oxide, thus, stress from die separation tends to generate cracks in the inter-layer dielectrics passing through the seal rings 11, and extending into the interior of the dice 10.
Various technologies can effectively but not completely eliminate damage to low-k dielectrics. It is difficult to predict and observe the occurrence of the cracks in low-k dielectrics. Cracks in inner layers of low-k dielectrics are particularly difficult to identify because they are typically invisible during visual inspection.
Thus, a damage monitoring technology is desirable.